The present invention relates to acoustical barriers and, more particularly, to sound absorbing structures adapted for use in occupied enclosures such as theaters, computer rooms, bowling centers and the like.
In order to maintain a comfortable noise level in rooms designed for occupancy by large numbers of people, the walls, floors and ceilings of such rooms are covered with an acoustical or sound absorbing material. Typically, floors are covered with carpeting and ceilings are fitted with acoustic ceiling tiles. However, these articles are unsuitable for use on the walls of such rooms. While the ceiling tiles possess acceptable sound absorbing capabilities, they are typically soft and susceptible to marring and damage by contact with the occupants of such rooms. Furthermore, ceiling tiles provide a poor appearance on walls. Carpeting, while possessing superior wear characteristics, is frequently unsuitable for use on the walls of rooms because its relatively high unit cost, relatively poor acoustic characteristics and unacceptable appearance.
Many attempts have been made to provide acoustic barriers which are either adapted to be mounted on the vertical walls of a room, or are designed to be freestanding and provide a vertical sound barrier. For example, the Humble U.S. Pat. No. 3,185,207 discloses an acoustic barrier which comprises a curtain of loose fabric which is attached to upper and lower brackets that are adapted to be mounted on the walls of a room. The brackets are shaped to form a saw tooth configuration so that the curtain they support hangs with a series of vertically extending, parallel pleats. A disadvantage with this structure is that the fabric alone does not possess high acoustic properties and is incapable of absorbing sound to a high degree. Another disadvantage of such a structure is that the fabric curtain hangs unsupported between the upper and lower brackets and often can sag or become ripped or wrinkled. In addition, the curtain material is often difficult to trim neatly at the top and bottom.
Another type of acoustic device is shown in the Steinberger U.S. Pat. No. 4,094,379. That device is a sound absorbing panel designed to be freestanding in a room and comprising a framework of a sound reflecting material, which preferably is transparent, forming a series of vertically extending pockets. Within each of a pockets is a strip of sound absorbing material which is positioned to absorb the sound reflected from the interior pocket walls of the framework.
A disadvantage with this type of structure is that it is relatively expensive to manufacture and contains a relatively small proportion of sound absorbing material. It should also appear that the device is not capable of absorbing soundwaves emanating from all directions, but rather is limited to soundwaves traveling in a relatively restricted area directly in front of the open pockets, since the sound waves must be reflected into the sound absorbing material.
An apparent disadvantage of both of the aforementioned structures is that only a single type of acoustic material is employed, and that material has a relatively uniform density. Since the type and density of acoustic material often determines the efficiency at which it absorbs sound in a given frequency range, a sound absorbing structure having a single sound absorbing material of a single or uniform density would be efficient at absorbing sound in only a few or perhaps a single frequency range, while operating less efficiently in absorbing sound in other frequency ranges.
Accordingly, there is a need for a sound absorbing structure adapted for use in occupied rooms which is sufficiently wear-resistant to withstand occasional contact with the occupants of the room, and yet is relatively inexpensive to manufacture and install. Furthermore, there is a need for such a sound absorbing structure which is capable of absorbing sound efficiently in a number of different frequency ranges. In addition, since such a sound absorbing panel will form an integral part of the design of an occupied room, it should present an aesthetically pleasing appearance and be capable of modification to suit different design and color schemes.